Multiple things make therapy work, and there is ample research to prove it. Studies consistently find a positive relationship with the therapist is the first step to achieving favorable outcomes. Having a safe place to simply be vulnerable without judgment or restriction can provide a powerful release. Being able to speak freely without interruption or fear of hurting another person feelings offers space to think and plan more clearly. These important things and more contribute to the positive outcome of therapy but are not what I believe is the most significant element.
If you are unaware of the choices you may have available, then the choices are not available to you. If you try to do your absolute best with the purest of intentions but use the same skills you used before, you are likely to get disappointing results. Bringing a trained therapist into the process offers new perspectives and the real possibility of productive results.
A therapist listens first to gain an understanding of your particular situation and needs. Next, we ask strategic questions designed to provoke fresh thinking about old dynamics. Finally, we offer psychoeducational tools designed to create new choices in thoughts and behaviors. For example, when someone comes in to see me after having an upsetting argument, we will review the events and surrounding emotions first. We might then re-process the interaction in a role-play format in order to model and practice different ways of saying and handling the same situation but with improved results.
If you need someone to work on your plumbing, you call a plumber. If you need someone to work on your mental health and happiness, call a therapist.